The present invention relates to a moldboard assembly for a motor grader and in particular, to a slide arrangement for the moldboard of the motor grader.
Motor graders are used to grade a base material such as gravel or sand to provide a generally planar or contoured surface. It can be used to provide a consistent grade to a surface such as a road bed or road shoulder. These operations are accomplished by the accurate positioning and control of a moldboard which is suspended beneath the grader frame. The moldboard is slidable relative to a drawbar used to secure the moldboard to the grader frame. The securement of the moldboard beneath the grader frame should be designed to avoid wobble or excess clearance in the support arrangement as poor tolerance variations can very significantly affect the control the operator has on the moldboard and the precision that is possible in a grading operation.
Motor graders perform relatively precise grading operations, however, they are a type of construction equipment and therefore, must be rugged and able to withstand very significant forces. The equipment is fairly robust in construction, however, the slide support of a moldboard and the requirement to maintain tight tolerances remain a difficult design problem. A moldboard, when in use, moves stone, dirt or other particulate material and this material can pass over the face of the moldboard and contaminate the slide arrangement which is located behind the moldboard. Such contamination can increase the wear of the slide bearings used to support the moldboard. Given the environment in which the grader is used and the nature of grading the slide support arrangement behind the moldboard will be subject to this type of contamination.
Most grader moldboards have two horizontal slide rails secured on longitudinal channel type members secured to the rear of the moldboard. These channel members are horizontal, reinforce the moldboard, and typically support the slide rails. With this arrangement, dirt or other material which passes over the moldboard can collect and remains in close proximity to the slide rail.
U.S. Pat. Nos. 5,678,800 and 5,076,370 are typical of the designs described above.
The present invention overcomes a number of disadvantages of these prior moldboard support arrangements.
A moldboard assembly according to the present invention comprises a moldboard, upper and lower slide rails secured to the moldboard by a series of vertical ribs spaced in the length of the moldboard and secured thereto. The ribs are secured to the rails at positions intermediate the length of the rails leaving an upper portion of one of the slide rails and a lower portion of the other slide rail unobstructed thereby defining bearing slide surfaces which traverse said ribs.
According to an aspect of the invention, the ribs are secured to a lower portion of the upper rail and an upper portion of the lower rail.
According to further aspect of the invention, each rib is spaced from an adjacent rib by a distance of less than 12 inches.
In a preferred aspect of the moldboard assembly, each rib spaces the slide rails outwardly of the moldboard defining a series of gaps between said ribs and between said slide rails and said moldboard.
According to yet a further aspect of the invention, the ribs are located to define a gap between adjacent ribs of less than 7 inches.